The present invention relates to the suspending of particles of a solid in a predetermined volume of liquid. More particularly, the invention deals with the suspending, or re-suspending, of particles when they are contained in a container, with a predetermined volume of liquid, the particles being partially collected in the form of a deposit or sediment immersed by the liquid at the bottom of the container.
The particles/liquid physical state previously described and defined is encountered in particular in certain analysis protocols or processes, especially biological ones, involving relatively heavy particles, for example each consisting of a magnetic substrate to which, for example, a reagent or an analyte is bound. In order to implement or continue the analysis process, it is essential to suspend or re-suspend the particles in the predetermined volume of liquid inside the container, since failing this the particles which have sedimented are removed from the analysis process and vitiate its result in terms of reliability, sensitivity and reproducibility.
Until now, these particles have been suspended by mechanical or fluidic means, for example by passing a gas stream through the liquid volume in the container, close to or in contact with the deposit of sedimented particles. An operation of this type generally leads to the formation of foam, at the level of the interface between the liquid volume and the atmosphere internal to the container; it therefore has to be controlled carefully in order to limit, and if possible eliminate, the formation of foam which, in particular, hampers any subsequent optical measurement taken through the container. In all, this suspending or re-suspending of particles starting from a deposit at the bottom of a container, with everything in a predetermined volume of liquid, represents an intricate and relatively time-consiming operation.